linux-kernel - [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt generation

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Message-Id: <cover.1466484019.git.panand@redhat.com>
Date:	Tue, 21 Jun 2016 10:25:34 +0530
From:	Pratyush Anand <panand@...hat.com>
To:	mingo@...nel.org, alexandre.belloni@...e-electrons.com
Cc:	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	prarit@...hat.com, Pratyush Anand <panand@...hat.com>
Subject: [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt generation

We have observed on few machines with rtc-cmos device that
hpet_rtc_interrupt() is called before cmos_do_probe() could call
hpet_rtc_timer_init(). It has not been observed during normal boot/reboot
of machines. It *sometime* happens when system is booted with kdump
secondary kernel. So, neither hpet_default_delta nor hpet_t1_cmp is
initialized by the time interrupt is raised in the given situation.
Therefore while loop of hpet_cnt_ahead() in hpet_rtc_timer_reinit() never
completes. This leads to "NMI watchdog: Watchdog detected hard LOCKUP on
cpu 0".

I am still clueless, how can an interrupt be raised before RTC is enabled.
But i do not have any idea about this device, so I am putting this patch as
RFC to get feedback from hpet/rtc-cmos developer. I am sure there would be
some better solution than this.

Pratyush Anand (2):
  rtc/hpet: Factorize hpet_rtc_timer_init()
  rtc/rtc-cmos: Initialize software counters before irq is registered

 arch/x86/include/asm/hpet.h |  2 ++
 arch/x86/kernel/hpet.c      | 41 +++++++++++++++++++++++++++++++++++------
 drivers/rtc/rtc-cmos.c      | 13 ++++++++++++-
 3 files changed, 49 insertions(+), 7 deletions(-)

-- 
2.5.5